The present invention relates to a gear coupler for coupling a gear to a shaft and more particularly to such a coupler which is comparatively easy to engage when the gear to be engaged is not freely rotatable when engagement is to be achieved.
For example, a number of different types of synchromesh couplers are known in which friction surfaces, which rotate with the gear and shaft respectively, are brought into contact with each other to synchronize the rotational speeds of the gear and shaft, and balking means are provided to prevent engagement between a coupling member associated with the shaft and a coupling member associated with the gear until synchronization has occurred.
While these different types of synchromesh couplers operate adequately in most circumstances, problems can arise when they are used in applications where large gear ratios are employed, for example, in the output stages of a transmission where range changing stages are employed.
In such applications, in order to complete the coupling of the gear to the shaft after synchronization, it may be necessary for the synchromesh coupler to generate sufficient rotational force to rotate the coupling member associated with the gear together with the gear itself and any associated meshing gears against a large torque reaction. Since the force required to rotate the coupling member associated with the gear and any associated meshing gears must be provided by the vehicle operator via a gear lever which controls the synchromesh coupler, this may lead to unacceptably high (even impossible) gear lever forces being required.
It is an object of the present invention to obviate or mitigate the foregoing problem.